臨時添加 IP 地址
首先，讓我們找到網卡的 IP 地址。在我的 Ubuntu 15.10 服務器版中，我只使用了一個網卡。
運行下面的命令找到 IP 地址：
sudo ip addr
樣例輸出：
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 08:00:27:2a:03:4b brd ff:ff:ff:ff:ff:ff
inet 192.168.1.103/24 brd 192.168.1.255 scope global enp0s3
valid_lft forever preferred_lft forever
inet6 fe80::a00:27ff:fe2a:34e/64 scope link
valid_lft forever preferred_lft forever
或
sudo ifconfig
樣例輸出：
enp0s3 Link encap:Ethernet HWaddr 08:00:27:2a:03:4b
inet addr:192.168.1.103 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::a00:27ff:fe2a:34e/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:186 errors:0 dropped:0 overruns:0 frame:0
TX packets:70 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:21872 (21.8 KB) TX bytes:9666 (9.6 KB)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:217 errors:0 dropped:0 overruns:0 frame:0
TX packets:217 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:38793 (38.7 KB) TX bytes:38793 (38.7 KB)
正如你在上面輸出中看到的，我的網卡名稱是 enp0s3，它的 IP 地址是 192.168.1.103。現在讓我們來為網卡添加一個新的 IP 地址，例如說 192.168.1.104。
打開你的終端并運行下面的命令添加額外的 IP。
sudo ip addr add 192.168.1.104/24 dev enp0s3
用命令檢查是否啟用了新的 IP：
sudo ip address show enp0s3
樣例輸出：
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 08:00:27:2a:03:4e brd ff:ff:ff:ff:ff:ff
inet 192.168.1.103/24 brd 192.168.1.255 scope global enp0s3
valid_lft forever preferred_lft forever
inet 192.168.1.104/24 scope global secondary enp0s3
valid_lft forever preferred_lft forever
inet6 fe80::a00:27ff:fe2a:34e/64 scope link
valid_lft forever preferred_lft forever
類似地，你可以添加任意數量的 IP 地址，只要你想要。讓我們 ping 一下這個 IP 地址驗證一下。
sudo ping 192.168.1.104
樣例輸出
PING 192.168.1.104 (192.168.1.104) 56(84) bytes of data.
64 bytes from 192.168.1.104: icmp_seq=1 ttl=64 time=0.901 ms
64 bytes from 192.168.1.104: icmp_seq=2 ttl=64 time=0.571 ms
64 bytes from 192.168.1.104: icmp_seq=3 ttl=64 time=0.521 ms
64 bytes from 192.168.1.104: icmp_seq=4 ttl=64 time=0.524 ms
好極了，它能工作！要刪除 IP，只需要運行：
sudo ip addr del 192.168.1.104/24 dev enp0s3
再檢查一下是否刪除了 IP。
sudo ip address show enp0s3
樣例輸出：
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 08:00:27:2a:03:4e brd ff:ff:ff:ff:ff:ff
inet 192.168.1.103/24 brd 192.168.1.255 scope global enp0s3
valid_lft forever preferred_lft forever
inet6 fe80::a00:27ff:fe2a:34e/64 scope link
valid_lft forever preferred_lft forever
可以看到已經沒有了！！正如你所知，重啟系統后這些設置會失效。那么怎么設置才能永久有效呢？這也很簡單。
添加永久 IP 地址
Ubuntu 系統的網卡配置文件是 /etc/network/interfaces。
讓我們來看看上面文件的具體內容。
sudo cat /etc/network/interfaces
輸出樣例：
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
source /etc/network/interfaces.d/*
# The loopback network interface
auto lo
iface lo inet loopback
# The primary network interface
auto enp0s3
iface enp0s3 inet dhcp
正如你在上面輸出中看到的，網卡啟用了 DHCP。現在，讓我們來分配一個額外的地址，例如 192.168.1.104/24。
編輯 /etc/network/interfaces：
sudo nano /etc/network/interfaces
如下添加額外的 IP 地址。
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
source /etc/network/interfaces.d/*
# The loopback network interface
auto lo
iface lo inet loopback
# The primary network interface
auto enp0s3
iface enp0s3 inet dhcp
iface enp0s3 inet static
address 192.168.1.104/24
保存并關閉文件。運行下面的命令使更改無需重啟即生效。
sudo ifdown enp0s3 && sudo ifup enp0s3
樣例輸出：
Killed old client process
Internet Systems Consortium DHCP Client 4.3.1
Copyright 2004-2014 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/
Listening on LPF/enp0s3/08:00:27:2a:03:4e
Sending on LPF/enp0s3/08:00:27:2a:03:4e
Sending on Socket/fallback
DHCPRELEASE on enp0s3 to 192.168.1.1 port 67 (xid=0x225f35)
Internet Systems Consortium DHCP Client 4.3.1
Copyright 2004-2014 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/
Listening on LPF/enp0s3/08:00:27:2a:03:4e
Sending on LPF/enp0s3/08:00:27:2a:03:4e
Sending on Socket/fallback
DHCPDISCOVER on enp0s3 to 255.255.255.255 port 67 interval 3 (xid=0xdfb94764)
DHCPREQUEST of 192.168.1.103 on enp0s3 to 255.255.255.255 port 67 (xid=0x6447b9df)
DHCPOFFER of 192.168.1.103 from 192.168.1.1
DHCPACK of 192.168.1.103 from 192.168.1.1
bound to 192.168.1.103 -- renewal in 35146 seconds.
注意：如果你從遠程連接到服務器，把上面的兩個命令放到一行中非常重要，因為第一個命令會斷掉你的連接。而采用這種方式可以保留你的 ssh 會話。現在，讓我們用下面的命令來檢查一下是否添加了新的 IP：
sudo ip address show enp0s3
輸出樣例：
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 08:00:27:2a:03:4e brd ff:ff:ff:ff:ff:ff
inet 192.168.1.103/24 brd 192.168.1.255 scope global enp0s3
valid_lft forever preferred_lft forever
inet 192.168.1.104/24 brd 192.168.1.255 scope global secondary enp0s3
valid_lft forever preferred_lft forever
inet6 fe80::a00:27ff:fe2a:34e/64 scope link
valid_lft forever preferred_lft forever
很好！我們已經添加了額外的 IP。再次 ping IP 地址進行驗證。
sudo ping 192.168.1.104
樣例輸出：
PING 192.168.1.104 (192.168.1.104) 56(84) bytes of data.
64 bytes from 192.168.1.104: icmp_seq=1 ttl=64 time=0.137 ms
64 bytes from 192.168.1.104: icmp_seq=2 ttl=64 time=0.050 ms
64 bytes from 192.168.1.104: icmp_seq=3 ttl=64 time=0.054 ms
64 bytes from 192.168.1.104: icmp_seq=4 ttl=64 time=0.067 ms
好極了！它能正常工作。就是這樣。
